Earnings Per Share

The following table sets forth the computation of basic and diluted earnings per share on net income (in thousands, except per share information):



	Three months ended March 31,
	2018		2017
Earnings:
Net income (numerator for basic and diluted calculations)	$	100,230	$	145,512
Shares:
Weighted average outstanding shares (denominator for basic calculation)	64,490		64,353
Equivalent shares from outstanding stock options	1,382		1,318
Denominator for diluted calculation	65,872		65,671
Earnings per share:
Basic	$	1.55	$	2.26
Diluted	$	1.52	$	2.22

The calculation of common equivalent shares does not include the impact of options having a strike or conversion price that exceeds the average stock price for the earnings period, as the result would be antidilutive. The calculation of common equivalent shares also excludes the impact of outstanding performance contingent shares, as the conditions necessary for their issuance have not been satisfied as of the end of the reporting period. For the three months ended March 31, 2018, approximately 0.2 million stock options and approximately 0.2 million performance contingent shares were excluded from the calculation. For the three months ended March 31, 2017, approximately 0.2 million stock options and approximately 0.5 million performance contingent shares were excluded from the calculation.